If someone had told our 14-year-old selves that as 40-year-old women, we’d have a publishing deal with Simon & Schuster, our first response probably would’ve been, “Ew, 40 is, like, soo old!” and then we might have tossed our Aqua Net infused curls over our shoulder pads and added, “That’s, like totally awesome, but HOW did we write three books together?”

The answer is: very carefully.

We’ve been friends since 1987, back when a gallon of gas was less than a buck and The Bangles topped the Billboard charts. Lisa was new the new girl in town and caught Liz’s eye with her humongous red-rimmed Sally Jesse Raphael- look-a-like eyeglasses and her fashion forward acid-wash overalls. And like many 14-year-old girls, we quickly learned we shared a mutual love of NKOTB and blue eye shadow and became instant BFFs bonding over our shared love of reading (Danielle Steel and Judy Blume topped our list of favorite authors) and writing, although we never dreamed one day we’d be here.

That came many, many years later.

And it’s a miracle we ended up co-authoring anything considering the infamous one act play incident of 1991. When our drama professor teamed us up to write a one-act play, we thought it was a fantastic idea. That was until we were sitting side-by-side at the word processor in Liz’s dorm room and somebody thought the murder weapon should be a gun and the other thought poison and well, let’s just say although it got written and was actually quite good if we do say so ourselves, we vowed to never collaborate on anything again.

Until we did—ten years later. (Thankfully neither us hold a grudge for very long…)

By then we were older, a lot wiser and had much straighter hair. We’d also been friends for so long that we’d developed our own shorthand, which came in quite handy while trying to navigate writing and editing 90,000 words without killing each other. We also came up with a few “rules” to keep us in check.

Liz & Lisa’s rules for co-writing

NEVER write side-by-side. (But if you must, don’t use a crappy word processor from 1991!)

If possible, collaborate in separate rooms (Or separate states, depending on the time of month).

Caffeinate early and often.

Limit any and all communication before 10am CST. (Did you know you can have “tone” over email?)

Count to 100 before reacting to each other’s constructive criticism. Andif that doesn’t curb an outburst, count backwards to 1.

But the most important rule of all? Don’t ever take yourself too seriously. Because we’ve worked too hard and been friends for too long to blow everything up over whether the word start is better than begin. (A real life example we have battled over, btw!)

Liz Fenton & Lisa Steinke are BFFs of 25+ years and co-authors of Your Perfect Life, Atria/Simon & Schuster on June 10, 2014.